Question 1

Which of the following best describes the difference between accuracy and precision in scientific measurements?

Accepted Answer

Accuracy refers to how close a measurement is to the true value, while precision refers to how close repeated measurements are to each other.

Question 2

A student measures the mass of a sample as 4.50 g, 4.48 g, and 4.51 g. The true mass is 5.00 g. Which statement is correct about the student's measurements?

Accepted Answer

The measurements are precise but not accurate.

Question 3

Which of the following is the correct scientific notation for the number 0.000345?

Accepted Answer

$$3.45 	imes 10$$^{-4}$$

Question 4

How many significant figures are in the measurement 0.02030 L?

Accepted Answer

4

Question 5

Which of the following statements about isotopes is correct?

Accepted Answer

Isotopes of an element have the same number of protons but different numbers of neutrons.

Question 6

Which element is a halogen?

Accepted Answer

Chlorine

Question 7

What is the formula for the ionic compound formed between magnesium and chlorine?

Accepted Answer

$$\mathrm{$$MgCl_2$$}$$

Question 8

Which of the following correctly names the compound $$\mathrm{Fe_2O_3}$$?

Accepted Answer

Iron(III) oxide

Question 9

What is the molar mass of $$\mathrm{Ca(OH)_2}$$? (Atomic masses: Ca = 40.08 g/mol, O = 16.00 g/mol, H = 1.01 g/mol)

Accepted Answer

74.10 g/mol

Question 10

How many molecules are in 0.250 mol of $$\mathrm{CO_2$}$$?

Accepted Answer

$$1.51 	imes 10$$^{23}$$

Question 11

Which of the following is a balanced equation for the combustion of methane ($$\mathrm{CH_4$}$$)?

Accepted Answer

$$\mathrm{CH_4$ + 2O_2 \rightarrow CO_2$ + 2H_2O}$$

Question 12

A sample contains 18.0 g of water ($$\mathrm{H_2O}). $$How many moles of water are present? (Molar mass of $$\mathrm{H_2O} = 18.0 g/$$mol)

Accepted Answer

1.00 mol

Question 13

Which of the following best describes a redox (oxidation-reduction) reaction?

Accepted Answer

A reaction in which electrons are transferred from one substance to another.

Question 14

What is the empirical formula of a compound that is 40.0% carbon, 6.7% hydrogen, and 53.3% oxygen by mass?

Accepted Answer

$$\mathrm{CH_2O}$$

Question 15

Which of the following is the correct Lewis structure for carbon dioxide ($$\mathrm{CO_2$}$$)?

Accepted Answer

O=C=O, with each O atom having two lone pairs

Question 16

A reaction has the following stoichiometry: $$2\mathrm{H_2$} + \mathrm{O_2$} \rightarrow 2\mathrm{H_2O}. If $$you start with 4.0 mol of $$\mathrm{H_2$}$$ and 2.0 mol of $$\mathrm{O_2$}$$, what is the limiting reagent?

Accepted Answer

Neither, both are in exact stoichiometric ratio

Question 17

Which of the following is the correct name for $$\mathrm{H_2SO_4}$$?

Accepted Answer

Sulfuric acid

Question 18

Which of the following best describes a double displacement reaction?

Accepted Answer

Two compounds exchange ions to form two new compounds.

Question 19

If 2.00 g of hydrogen reacts with excess oxygen to form water, how many grams of water are produced? (Molar mass: H = 1.01 g/mol, O = 16.00 g/mol)

Accepted Answer

Question 20

Which of the following is a property of metals?

Accepted Answer

They are good conductors of electricity.

Exam 1 Review: Measurements, Atoms, Compounds, and Chemical Reactions (GOB Chemistry)

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